of the Fishery Board for Scotland. 



15 



temperature of the water and the amount of food material present in it ; 

 and to determine the extent, places, and seasons of spawning. A scheme 

 was accordingly prepared on which the investigation might proceed, 

 comprising the following : — (1) A study of all the statistics that could be 

 obtained for each of the Clyde fishery districts in former years, going as 

 far back as possible, and of the reports and remarks of the Fishery 

 Officers. (2) Serial observations at intervals on the temperature of the 

 water at different depths. (3) Simultaneous collections of the plankton 

 or floating organisms upon which the herring principally feeds. (4) The 

 marking and liberation of herrings when possible, with the view of 

 ascertaining their movements. (5) The examination of large numbers of 

 herrings periodically from various parts of the Clyde, to determine their 

 feeding, the condition of the reproductive organs as to maturity, and the 

 rapidity with which these organs develop and become fully mature. 

 Special nets have also been used to ascertain the presence of small post- 

 larval and young herrings in the loch, and a research was made by 

 Professor Milroy on the chemical composition of the herrings at different 

 sexual stages, the results of which have already appeared.* 



Since the range of movement of a shoal of herrings at different 

 periods of the year on any part of the coast is unknown, but is believed 

 to be considerable, it was desired that the investigation might cover at 

 least the whole of the sea area of the Clyde. It was obviously of import- 

 ance that the observations should not be confined to Loch Fyne, but 

 should include the other parts of the Firth, and particularly the channels 

 by which the herrings 6nter or leave the loch. Comparison of the 

 temperatures and of the plankton at any given time in these areas would 

 be of value. It was, however, found to be impossible to extend the 

 observations in the way indicated, owing to the want of means, and, with 

 the exception noted below, the temperature and plankton observations 

 have been limited to Loch Fyne, a small yacht and boats being hired for 

 the purpose, since no steamer is at the disposal of the Board for such 

 work in the Clyde. 



A number of " Stations" were fixed upon at intervals of a few miles, 

 extending from near the mouth of the loch to the neighbourhood of 

 Inverara}'. At each Station the temperature of the water was determined 

 at intervals of nfteen fathoms from the surface to the bottom, collections 

 of plankton being also made at the same levels, and the observations 

 were carried on as far as possible in each month throughout the year. 

 In addition to these Captain Alexander, of the superintending Fishery 

 cruiser "Vigilant." has taken observations of the temperature of the 

 water (without plankton collections) at the surface, bottom, and one 

 intermediate depth, at various parts of the Firth of Clyde, and these 

 records, with the sanction of the Board, have been placed at disposal. 



The various investigations noted above are being continued, and will 

 be reported on later. This part of the report deals with the fluctuations 

 in the yield of the fishery from year to year, and is based upon the 

 statistics which have been collected by the Fishery Officers of the various 

 districts since 1809, but mainly since 1854, as more fully explained 

 below. 



The Methods of Fishing. 



In the Firth of Clyde herrings are captured by three methods of 

 fishing — viz., by drift-nets, seine-nets, and set-nets or ground-nets, of 

 which the two former, and especially the seine-net, are the more impor- 



*See Twenty -Fourth Annual Report, Part III., p. 83. 



